On Mon, Jul 07, 2014 at 09:53:58AM +0900, Minchan Kim wrote:
> We don't need to split THP page when MADV_FREE syscall is
> called. It could be done when VM decide really frees it so
> we could reduce the number of THP split.
>
> Signed-off-by: Minchan Kim <minc...@kernel.org>
> ---
> include/linux/huge_mm.h | 3 +++
> mm/huge_memory.c | 25 +++++++++++++++++++++++++
> mm/madvise.c | 19 +++++++++++++++++--
> mm/rmap.c | 4 ++++
> mm/vmscan.c | 24 ++++++++++++++++--------
> 5 files changed, 65 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index 63579cb8d3dc..f0d37238cf8f 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -19,6 +19,9 @@ extern struct page *follow_trans_huge_pmd(struct
> vm_area_struct *vma,
> unsigned long addr,
> pmd_t *pmd,
> unsigned int flags);
> +extern int madvise_free_pmd(struct mmu_gather *tlb,
> + struct vm_area_struct *vma,
> + pmd_t *pmd, unsigned long addr);
> extern int zap_huge_pmd(struct mmu_gather *tlb,
> struct vm_area_struct *vma,
> pmd_t *pmd, unsigned long addr);
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 5d562a9fe931..2a70069dcfc0 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -1384,6 +1384,31 @@ out:
> return 0;
> }
>
> +int madvise_free_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
> + pmd_t *pmd, unsigned long addr)
> +{
> + spinlock_t *ptl;
> + int ret = 0;
> +
> + if (__pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
> + pmd_t orig_pmd;
> + struct mm_struct *mm = vma->vm_mm;
> +
> + /* No hugepage in swapcache */
> + VM_BUG_ON(PageSwapCache(pmd_page(orig_pmd)));
VM_BUG_ON_PAGE() ?
> +
> + orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd);
> + orig_pmd = pmd_mkold(orig_pmd);
> + orig_pmd = pmd_mkclean(orig_pmd);
> +
> + set_pmd_at(mm, addr, pmd, orig_pmd);
> + tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
> + spin_unlock(ptl);
> + ret = 1;
> + }
> + return ret;
> +}
> +
> int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
> pmd_t *pmd, unsigned long addr)
> {
> diff --git a/mm/madvise.c b/mm/madvise.c
> index 372a25a8ea82..3c99919ee094 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -320,8 +320,23 @@ static inline unsigned long
> madvise_free_pmd_range(struct mmu_gather *tlb,
> * if the range covers.
> */
> next = pmd_addr_end(addr, end);
> - if (pmd_trans_huge(*pmd))
> - split_huge_page_pmd(vma, addr, pmd);
> + if (pmd_trans_huge(*pmd)) {
> + if (next - addr != HPAGE_PMD_SIZE) {
> +#ifdef CONFIG_DEBUG_VM
> + if (!rwsem_is_locked(&tlb->mm->mmap_sem)) {
> + pr_err("%s: mmap_sem is unlocked!
> addr=0x%lx end=0x%lx vma->vm_start=0x%lx vma->vm_end=0x%lx\n",
> + __func__, addr, end,
> + vma->vm_start,
> + vma->vm_end);
> + BUG();
> + }
> +#endif
> + split_huge_page_pmd(vma, addr, pmd);
> + } else if (madvise_free_pmd(tlb, vma, pmd, addr))
> + goto next;
> + /* fall through */
> + }
> +
> /*
> * Here there can be other concurrent MADV_DONTNEED or
> * trans huge page faults running, and if the pmd is
> diff --git a/mm/rmap.c b/mm/rmap.c
> index ee495d84c8b3..3c415eb8b6f0 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -702,6 +702,10 @@ static int page_referenced_one(struct page *page, struct
> vm_area_struct *vma,
> /* go ahead even if the pmd is pmd_trans_splitting() */
> if (pmdp_clear_flush_young_notify(vma, address, pmd))
> referenced++;
> +
> + if (pmd_dirty(*pmd))
> + dirty++;
> +
> spin_unlock(ptl);
> } else {
> pte_t *pte;
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index f7a45600846f..4e15babf4414 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -971,15 +971,23 @@ static unsigned long shrink_page_list(struct list_head
> *page_list,
> * Anonymous process memory has backing store?
> * Try to allocate it some swap space here.
> */
> - if (PageAnon(page) && !PageSwapCache(page) && !freeable) {
> - if (!(sc->gfp_mask & __GFP_IO))
> - goto keep_locked;
> - if (!add_to_swap(page, page_list))
> - goto activate_locked;
> - may_enter_fs = 1;
> + if (PageAnon(page) && !PageSwapCache(page)) {
> + if (!freeable) {
> + if (!(sc->gfp_mask & __GFP_IO))
> + goto keep_locked;
> + if (!add_to_swap(page, page_list))
> + goto activate_locked;
> + may_enter_fs = 1;
>
> - /* Adding to swap updated mapping */
> - mapping = page_mapping(page);
> + /* Adding to swap updated mapping */
> + mapping = page_mapping(page);
> + } else {
> + if (unlikely(PageTransHuge(page))) {
> + if (unlikely(split_huge_page_to_list(
> + page, page_list)))
> + goto keep_locked;
Hm. It would be better to free the huge page without splitting.
It shouldn't be a big deal: walk over rmap and zap all pmds.
Or I miss something?
> + }
> + }
> }
>
> /*
> --
> 2.0.0
>
> --
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--
Kirill A. Shutemov
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